Transistors may be used as switches e.g. within switched-mode power supplies (e.g. buck converters, boost converters or buck-boost converters). In the context of such applications, the transistors are switched between the on-state and the off-state of the transistor in a periodic manner in accordance to a commutation cycle rate. The commutation cycle rate is typically in the range of 100 kHz (for high voltage power electronic applications) and in the range of several MHz (for low voltage applications), and the ratio of the length of the on-state and the length of the off-state (referred to as the duty cycle) may be used to control the conversion ratio (between the input voltage and the output voltage) of the switched-mode power supply.
The transition from the on-state to the off-state and vice versa may be controlled using a driver signal (i.e. a signal to the gate of the transistor) generated by a driver circuit. The driver circuit may be separate from the power transistor, i.e. the transistor may be external to the driver circuit. In other words, the driver circuit may be implemented in a dedicated integrated circuit, separate from the power transistor.
If an external transistor is switched on fast (i.e. switched on with a steep step function of the driver signal), the current through the external transistor may start to oscillate due to parasitic inductors and capacitors of the external transistor (and the neighbouring circuitry of the external transistor, e.g. the circuitry of the switched mode power supply). In other words, subject to the receipt of a transient drive signal (e.g. a pulsed drive signal) from the driver circuit putting the external power transistor to the on-state, the parasitic capacitances and inductances in the external power transistor and the circuitry in the neighborhood of the external power transistor may cause ringing artifacts on the source current of the external transistor. For measuring the ringing of the source current, an external resistor, as well as an additional measurement pin within the driver circuit may be used. This allows for an explicit measurement of the presence of ringing artifacts, however, the measurement circuitry also requires an additional external resistor, as well as an additional pin within the driver circuit. Hence, the explicit measurement of ringing of the source current at the external power transistor is relatively complex.
The present document addresses the above mentioned shortcomings of driver circuits causing ringing artifacts at an external power transistor. In particular, the present document describes a method and system for detecting and compensating ringing artefacts at the external power transistor directly within the driver circuit, thereby removing the need for additional external components (such as an external resistor) and the need for an additional measurement pin at the driver circuit.